JPA+mysql+servlet实现的连接操作数据库的小例子

kinila

　　persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">
<persistence-unit name="mysql" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>java:comp/env/jdbc/mysql</jta-data-source>
<class>com.chinasoft.database2.Persion</class>
<properties>
<property name="hibernate.show_sql" value="true"></property>
</properties>
</persistence-unit>
</persistence>
　　tomcat中server.xml配置：

  <Context path="/DatabaseTest" docBase="/DatabaseTest"  reloadable="false" crossContext="true">
<Resource name="jdbc/mysql"   auth="Container"  type="javax.sql.DataSource"  
maxActive="5"   maxIdle="2"   maxWait="10000"   removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost/lpm?user=root&amp;password=" />
</Context>
　　建一个实体Persion类：

package com.chinasoft.database2;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="persion")
public class Persion {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private java.lang.Long userid;
private java.lang.String name;

public java.lang.Long getUserid() {
return userid;
}
public void setUserid(java.lang.Long userid) {
this.userid = userid;
}
public java.lang.String getName() {
return name;
}
public void setName(java.lang.String name) {
this.name = name;
}
}
　　建一个servlet类：

public class Start extends HttpServlet {
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
   EntityManagerFactory entityfactory = null;
   EntityTransaction  t=null;
   EntityManager em=null;
  try{
   entityfactory = Persistence.createEntityManagerFactory("mysql");
   em=entityfactory.createEntityManager();
   
   Query query=em.createQuery("from Persion");
   List list=query.getResultList();
   Iterator iter=list.iterator();
   while(iter.hasNext()){
    Persion persion=(Persion) iter.next();
    System.out.println(persion.getName());
   }
   
   
      t=em.getTransaction();
   t.begin();
   Persion p=new Persion();
   p.setName("abc");
   em.persist(p);
   t.commit();
  }catch(Exception e){
   e.printStackTrace();
   t.rollback();
  }
  em.close();
  entityfactory.close();
 }
}